1. Field of the Invention
The present invention generally relates to a radio communication method and a radio communication apparatus capable of transferring data among a plurality of nodes within a wireless network. More particularly, this invention relates to a radio communication method and a radio communication apparatus which can transfer a fixed length data block among respective nodes by using a predetermined time slot of a plurality of time slots provided within respective consecutive cycles and in which a control node can manage the transmission of isochronous communication data of each node at the unit of one cycle or a plurality of cycles, thereby making it possible to improve a transmission efficiency.
2. Description of the Related Art
Recently, as portable devices such as a notebook-size portable computer and an electronic notebook become widespread, a variety of analog and digital interfaces had hitherto been made wireless and high-speed. Particularly in the computers fields, a variety of analog and digital interfaces have been so far made wireless and high-speed actively. For example, by using technologies represented by a wireless LAN (local area network) and IrDA (infrared data association), a network based on a non-contact connection has been constructed between stationary devices as well as portable devices.
In the wireless LAN, for example, a communication among a plurality of nodes is made possible by using an access control protocol called a CSMA (carrier sense multiple access). Moreover, in the IrDA, a communication between two nodes is made possible by using an access control protocol called an IrLAP (infrared link access protocol).
However, when recent high-speed serial buses represented by USB (universal serial bus) and IEEE 1394 serial bus, for example, are made wireless, these access technologies cannot be used as they are. As is well-known, these high-speed serial buses are adapted to support a transfer system called an isochronous transfer system in order to transmit application data which may attach importance to a real-time property, such as AV (audio-visual) data. This isochronous transfer system is a transfer system in which a transfer of data of a constant data amount at a constant cycle, which become important factors for achieving a real-time property of device, can be realized by guaranteeing a data transfer width and a data transfer time.
In order to realize such transfer system by a wireless network comprising a plurality of nodes, transmission nodes should be frequently switched so as to guarantee transfer widths and transfer times of individual data transmitted from a plurality of nodes. For this reason, the above-mentioned access control protocol for the IrLAP which is used in a one-to-one relationship cannot be used as it is, and also the above-mentioned access control protocol called CSMA in which the transfer width is guaranteed after the state in which a space is not yet used was detected cannot be used as it is.
The assignee of the present application has previously proposed the above-mentioned wireless network in which a fixed-length data block is transferred between respective nodes by effectively utilizing a predetermined time slot of a plurality of time slots provided within each consecutive cycle (see Japanese laid-open patent application No. 9-267045). In this case, when a packet with a fixed data length (isochronous communication data) is transferred like the isochronous transfer system, the processing for controlling a node switching timing, or the like can be simplified by reserving several time slots.
However, the length of packet transmitted in actual practice is not always identical to an integral multiple of a length of this fixed-length data block. Let it now be assumed that a represents a length of data block and the length of packet is slightly longer than the length a, i.e. (a+b)(a greater than  greater than b). Then, in order to transfer the very small packet remaining portion b, another one data block (one time slot) should be used. This means that, if the remaining portion (axe2x88x92b) has no transmission data, then a transmission efficiency is unavoidably lowered on the whole.
It is an object of the present invention to provide a radio communication method and a radio communication apparatus in which a fixed-length data block is transferred between respective nodes by using a predetermined time slot of a plurality of time slots provided within each consecutive cycle and which can improve a transmission efficiency.
According to an aspect of the present invention, there is provided a radio communication method of making a communication within a wireless network comprising one control node and more than one controlled nodes controlled by the control node. This radio communication method is comprised of a communication control process in which the control node controls the transmission of each node such that a fixed-length data block may be transferred between the nodes by using a predetermined time slot of a plurality of time slots provided within each consecutive cycle, wherein the control node manages the transmission of isochronous communication data of each node at the unit of one cycle of a plurality of cycles in the transmission control process.
In accordance with another aspect of the present invention, there is provided a radio communication apparatus which is comprised of one control node and more than one controlled nodes controlled by the control node and in which a fixed-data block is transferred between the nodes by using a predetermined time slot of a plurality of time slots provided within each consecutive cycle, wherein the control node includes a transmission management means for managing the transmission of isochronous communication data of each node at the unit of one cycle or a plurality of cycles.
In the present invention, the wireless network comprises one control node and more than one controlled nodes controlled by this control node, and the present invention relates to a communication effected within this wireless network. The transmission in each node is controlled by the control node, and a fixed-length data block is transferred between the respective nodes by using a predetermined slot of a plurality of time slots provided with each consecutive cycle.
In this case, the control node manages the transmission of isochronous communication data of each node at the unit of one cycle or a plurality of cycles. This unit information is reported to the control node from each node, for example. Each node calculates a total data length of isochronous communication data transmitted within one cycle, for example, calculates a remainder by dividing this total data length with a data length of the data block, and obtains the unit information by using this remainder.
Since the control node manages the transmission of isochronous communication data of each node at the unit of one cycle or a plurality of cycles as described above, the portions in which data block becomes useless can be reduced, thereby making it possible to improve a transmission efficiency.